US5520726A - Casting investment compounds - Google Patents
Casting investment compounds Download PDFInfo
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- US5520726A US5520726A US08/252,868 US25286894A US5520726A US 5520726 A US5520726 A US 5520726A US 25286894 A US25286894 A US 25286894A US 5520726 A US5520726 A US 5520726A
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- zeolite
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- 150000001875 compounds Chemical class 0.000 title claims abstract description 62
- 238000005266 casting Methods 0.000 title claims description 20
- 239000010457 zeolite Substances 0.000 claims abstract description 61
- 229910021536 Zeolite Inorganic materials 0.000 claims description 36
- 239000000843 powder Substances 0.000 claims description 35
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 claims description 30
- 239000000203 mixture Substances 0.000 claims description 28
- 238000002156 mixing Methods 0.000 claims description 12
- 239000012530 fluid Substances 0.000 claims description 9
- 239000011230 binding agent Substances 0.000 claims description 3
- 239000011819 refractory material Substances 0.000 claims description 3
- 230000002378 acidificating effect Effects 0.000 claims description 2
- 239000012013 faujasite Substances 0.000 claims description 2
- 230000001476 alcoholic effect Effects 0.000 claims 1
- 238000002360 preparation method Methods 0.000 abstract description 6
- 238000005058 metal casting Methods 0.000 abstract description 4
- 238000005495 investment casting Methods 0.000 abstract description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 50
- 239000010453 quartz Substances 0.000 description 26
- 206010037844 rash Diseases 0.000 description 23
- 238000006253 efflorescence Methods 0.000 description 20
- 229910052906 cristobalite Inorganic materials 0.000 description 13
- 229920001296 polysiloxane Polymers 0.000 description 11
- 239000000975 dye Substances 0.000 description 10
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 10
- 241000212342 Sium Species 0.000 description 9
- -1 for example Substances 0.000 description 9
- 239000000395 magnesium oxide Substances 0.000 description 8
- 239000000463 material Substances 0.000 description 8
- 229920001817 Agar Polymers 0.000 description 7
- 229910019142 PO4 Inorganic materials 0.000 description 7
- 238000009472 formulation Methods 0.000 description 7
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 7
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 7
- 239000006004 Quartz sand Substances 0.000 description 6
- 239000008272 agar Substances 0.000 description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 6
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 6
- 238000000034 method Methods 0.000 description 6
- 235000021317 phosphate Nutrition 0.000 description 6
- 150000001768 cations Chemical class 0.000 description 5
- 229910052681 coesite Inorganic materials 0.000 description 5
- 229910052761 rare earth metal Inorganic materials 0.000 description 5
- 150000002910 rare earth metals Chemical class 0.000 description 5
- 239000000377 silicon dioxide Substances 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 229910052682 stishovite Inorganic materials 0.000 description 5
- 229910052905 tridymite Inorganic materials 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 239000011777 magnesium Substances 0.000 description 4
- 238000007711 solidification Methods 0.000 description 4
- 230000008023 solidification Effects 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 239000000654 additive Substances 0.000 description 3
- 230000002411 adverse Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000000499 gel Substances 0.000 description 3
- 229910052749 magnesium Inorganic materials 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000011505 plaster Substances 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 229910000318 alkali metal phosphate Inorganic materials 0.000 description 2
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- CBFCDTFDPHXCNY-UHFFFAOYSA-N icosane Chemical compound CCCCCCCCCCCCCCCCCCCC CBFCDTFDPHXCNY-UHFFFAOYSA-N 0.000 description 2
- 239000012266 salt solution Substances 0.000 description 2
- 229910018404 Al2 O3 Inorganic materials 0.000 description 1
- 239000004254 Ammonium phosphate Substances 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 229910017344 Fe2 O3 Inorganic materials 0.000 description 1
- 229910017958 MgNH Inorganic materials 0.000 description 1
- 229910003202 NH4 Inorganic materials 0.000 description 1
- 206010039509 Scab Diseases 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 150000001342 alkaline earth metals Chemical class 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 235000019289 ammonium phosphates Nutrition 0.000 description 1
- 150000003863 ammonium salts Chemical class 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005422 blasting Methods 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- ZOMBKNNSYQHRCA-UHFFFAOYSA-J calcium sulfate hemihydrate Chemical compound O.[Ca+2].[Ca+2].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O ZOMBKNNSYQHRCA-UHFFFAOYSA-J 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000004040 coloring Methods 0.000 description 1
- 239000012612 commercial material Substances 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000005548 dental material Substances 0.000 description 1
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000002209 hydrophobic effect Effects 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 229910052909 inorganic silicate Inorganic materials 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 239000004137 magnesium phosphate Substances 0.000 description 1
- 235000010994 magnesium phosphates Nutrition 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 229910001092 metal group alloy Inorganic materials 0.000 description 1
- 239000002808 molecular sieve Substances 0.000 description 1
- 239000000206 moulding compound Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 229910052701 rubidium Inorganic materials 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- 229910052567 struvite Inorganic materials 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000007669 thermal treatment Methods 0.000 description 1
- 230000003313 weakening effect Effects 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
Definitions
- the present invention relates to investment compounds containing zeolites and to models and moulds made from these.
- the investment compounds according to the invention are used in metal casting, preferably in the preparation of precision castings.
- this object is achieved by the addition of zeolites to the investment compound compositions known per se.
- the investment compounds according to the invention are in general used in metal casting, for example in the restoration and copying of valuable metal objects.
- a preferred field of application of the investment compounds according to the invention is dental engineering, where tooth replacement parts are made with the aid of casting investment compounds.
- wax modellings which reproduce the shape of the tooth restoration which is to be cast, are invested with the aid of such a compound, or investment compound models are produced, such as, for example, in the prepartion of model-casting structures for partial tooth prostheses.
- the wax modellings are heated together with the investment compounds and thus burn off without a residue.
- the investment compound compositions are known per se. They consist as a rule of a powder which is composed of refractory materials, such as, for example, quartz or cristobalite, and a binder, such as, for example, magnesium oxide/ammonium phosphate or calcium sulphate hemihydrate, and of a mixing fluid, such as, for example, water or a silica sol solution.
- phosphate-bonded investment compounds which essentially contain magnesium oxide and phosphates as binders and quartz and cristobalite as refractory materials.
- the mixing fluid used for this purpose is frequently a silica sol solution.
- the reactions during the solidification and heating of the mixed investment compound can be represented by the following equations:
- the alkalis presumably originate mainly from the additives which are added for stabilization to the silica sol solutions used as mixing fluids, or they originate from the alkali metal phosphate additives which are added to the investment compound powder formulations for controlling the setting kinetics.
- EP-0,417,527 Another attempt at suppressing the "efflorescences" is described in EP-0,417,527.
- the addition of 0.01 to 10% by weight of at least one solid organic acid soluble in water and/or alcohol and having 2 to 10 carbon atoms is recommended in the preparation of casting moulds from casting investment compounds.
- the zeolites are preferably employed in quantities from 0.1 to 10.0% by weight (relative to the total pulverulent compound before the addition of the mixing fluid), particularly preferably in quantities from 0.4 to 5.0% by weight.
- Zeolites to be employed preferably according to the invention are characterized by the general formula (I):
- M 1 denotes one equivalent of an exchangeable cation, whose number corresponds to the proportion of M 2 ,
- M 2 denotes a trivalent element which, together with the Si, forms the oxide skeleton of the zeolite
- q denotes the quantity of the adsorbed water.
- zeolites are crystalline alumosilicates which are built up from a network of tetrahedra of SiO 4 and M 2 O 4 .
- the individual tetrahedra are mutually linked by oxygen bridges via the corners of the tetrahedra and form a spatial network which is evenly penetrated by channels and voids.
- the individual zeolite structures differ by the arrangement and size of the channels and voids and by their composition.
- exchangeable cations are incorporated.
- the adsorbed water phase qH 2 O is reversibly removable, without the skeleton losing its structure.
- M 2 is in many cases aluminium, but it can also be partially or wholly substituted by other trivalent elements.
- zeolites are particularly suitable for the process according to the invention: faujasites, mordenites, zeolite A, zeolite ⁇ , zeolite ⁇ , zeolite L, offretite, ZSM 12, pentasils, PSH-3, ZSM 22, ZSM 23, ZSM 48, EU-1, zeolite T, chabasites, gmelinites, ferrierites, zeolite rho, ZK-5 and others.
- the zeolites suitable for the process according to the invention can contain alkali metal cations, such as, for example, Li, Na, K or Rb, or alkaline earth metal cations, such as, for example, Mg, Ca or Sr, or else other cations, such as, for example, H, NH 4 , Zn, Cu, Ni, Co, Mn, rare earth metals and others. Mixed forms can also be used.
- alkali metal cations such as, for example, Li, Na, K or Rb
- alkaline earth metal cations such as, for example, Mg, Ca or Sr
- other cations such as, for example, H, NH 4 , Zn, Cu, Ni, Co, Mn, rare earth metals and others.
- Mixed forms can also be used.
- the zeolites used according to the invention are those in which at least a part of the metal cations has been exchanged for hydrogen ions, preferably 50 to 100%, particularly preferably 80 to 100% of all the exchangeable metal cations originally present.
- zeolites having a multiplicity of acidic centres such as are formed, for example, by treating zeolites of the faujasite structure with ammonium salt solutions or rare earth salt solutions and subsequent thermal treatment.
- the added quantity of the zeolites described above is preferably a quantity from 0.1 to 10% by weight.
- the efflorescence-preventing effect of various zeolite types is pronounced to different extents. Simple experiments allow optimum dosage.
- the zeolites containing alkali metal, alkaline earth metal or rare earth metal are very effective.
- the most effective zeolites are those of the H-zeolite Y-type.
- H-zeolite Y 0.3 to 1.5% by weight was found to be a particularly preferred quantity for obtaining the efflorescence-preventing effect and, for the zeolites containing a rare earth metal, the particularly preferred added quantity is 0.7 to 2.0% by weight.
- the basic formulations of the investment compound powders according to the invention can be prepared in a conventional manner known per se in a suitable mixing unit, for example a Nauta mixer, Lodige mixer or the like, in which the pulverulent additives including the zeolites are mixed together one after the other. It is also possible, however, to prepare master mixtures which contain the zeolite, and to mix in these master mixtures. Furthermore, it is also possible with the zeolite-containing investment compound formulations according to the invention, which have been described, to spray these in a manner known per se with isoparaffins, without losing the desired properties described above, for example in order to improve their flow properties once again.
- the zeolite-containing investment compound powder mixtures according to the invention show no disadvantages as compared with investment compound mixtures not containing zeolite. No changes in the setting time and setting temperature, relevant to processing, occur. The good gel compatibility is unchanged. The good mechanical strength of the casting muffle or of the model made from the investment compound is unchanged, and the same applies to the expansion on setting, which is an important parameter for the degree of the dimensional accuracy of the casting obtained later.
- the investment compound formulations according to the invention can be used, in particular, both opposite duplicating silicone and opposite an agar duplicating composition.
- the expansion on setting, the processing time and the compressive strength are determined analogously to DIN 13919, part 2, June 1984.
- the setting time is the point in time at which the setting temperature reaches the temperature maximum.
- the tendency to efflorescence was tested by mixing the investment compound powders described with a commercially available silica sol mixing fluid (Levotherm mixing fluid) and pouring the mixed casting investment compound paste into an addition-crosslinked silicone duplicating moulding compound (for example of Tecnovil commercial material), by releasing the solidified investment compound model and assessing the investment compound surface 24 hours after mould release and standing in room air.
- the investment compound powder composition is prepared by homogeneous mixing of the individual components in a slow-blade mixer (Lodige mixer), a conical truncated cone mixer with revolving screw (Nauta mixer) or in tumble mixers, but other suitable mixer units can in principle also be used.
- a slow-blade mixer Lidige mixer
- a conical truncated cone mixer with revolving screw Neta mixer
- tumble mixers revolving screw
- the quartz powder used in the examples has an SiO 2 content of >99% with a total residue of about 90% by volume at a grain diameter of 2 ⁇ m, measured by means of a Cilas granulometer, and a total residue of about 89% by weight at a sinking velocity-equivalent diameter of 2.5 ⁇ m, measured by sedimentation analysis by means of a Sedi Graph 5100.
- a usable type of quartz sand has an SiO 2 content of >99% at a mean grain size of 0.28 mm.
- a cristobalite powder type which can be used shows, at an SiO 2 content of >99%, a grain size distribution by screen analysis of (diameter/proportion in % by weight) >200 ⁇ m/0.5, >100/5, >63/20, >40/44, ⁇ 40/30.5 and a BET surface area of 0.9 m 2 /g.
- the phosphates used are Fabutit 746 (made by Budenheim) in a addition to a little Fabutit GI/66A (made by Budenheim), and the magnesium oxide used is Dynamag K (made by Huls) in addition to a little Mag Chem 40 (Gobel & Pfrengle).
- a red dyestuff made by Conrads
- a red dyestuff which on average has the following composition: 53.9-51.6% of SiO 2 , 24.0-27.4% of Al 2 O 3 , 6.3-11.6% of Fe 2 O 3 and 0.8-0.21% of MgO, loss on ignition 12.5-8.5%.
- the zeolite addition according to the invention does not cause any adverse influence on the compatibility with duplicating gel and on the expansion on setting.
- the mechanical properties have been improved due to the zeolithe addition.
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Dental Preparations (AREA)
- Mold Materials And Core Materials (AREA)
- Dental Prosthetics (AREA)
- Molds, Cores, And Manufacturing Methods Thereof (AREA)
- Adornments (AREA)
Abstract
The present invention relates to investment compounds containing zeolites and to models and moulds made from these. The investment compounds according to the invention are used in metal casting, preferably in the preparation of precision castings.
Description
The present invention relates to investment compounds containing zeolites and to models and moulds made from these. The investment compounds according to the invention are used in metal casting, preferably in the preparation of precision castings.
In the preparation of metal castings, the important point in many cases is as identical as possible a reproduction of details, such as fine surface structures. Particularly in cases, in which the original is not available for an unlimited time, a cast, for example a silicone cast, is then first made, with the aid of which a so-called master model, for example of plaster, is produced.
From the latter, another cast, in most cases of agar or silicone, is made, with the aid of which a copy of the master model of plaster or, if parts exactly fitting to the original are to be made, is produced from an investment compound.
In the latter case, in particular opposite the hydrophobic silicone surfaces, a formation of fine, salt-like crusts takes place on the surface of the model made from an investment compound, namely the so-called efflorescences. The attempt to remove these, for example mechanically, frequently causes damage which, like the efflorescences which have not been removed, is itself the cause of defects on the cast object produced later.
It was the object underlying the present invention to produce casting investment compounds which are free of efflorescences but possess unchanged good mechanical properties.
According to the invention, this object is achieved by the addition of zeolites to the investment compound compositions known per se. The investment compounds according to the invention are in general used in metal casting, for example in the restoration and copying of valuable metal objects. A preferred field of application of the investment compounds according to the invention is dental engineering, where tooth replacement parts are made with the aid of casting investment compounds. In this case, wax modellings, which reproduce the shape of the tooth restoration which is to be cast, are invested with the aid of such a compound, or investment compound models are produced, such as, for example, in the prepartion of model-casting structures for partial tooth prostheses. The wax modellings are heated together with the investment compounds and thus burn off without a residue. As a result, cavities are formed in which the dental restoration materials, as a rule metal alloys, are cast. After hardening and cooling of the restoration materials, the investment compounds are removed and the cast tooth replacement part is obtained which, after further working steps, such as blasting, polishing, veneering and the like, is available for incorporation into the denture. The investment compound compositions are known per se. They consist as a rule of a powder which is composed of refractory materials, such as, for example, quartz or cristobalite, and a binder, such as, for example, magnesium oxide/ammonium phosphate or calcium sulphate hemihydrate, and of a mixing fluid, such as, for example, water or a silica sol solution. Frequently, so-called phosphate-bonded investment compounds are used which essentially contain magnesium oxide and phosphates as binders and quartz and cristobalite as refractory materials. The mixing fluid used for this purpose is frequently a silica sol solution. The reactions during the solidification and heating of the mixed investment compound can be represented by the following equations:
Solidification: NH.sub.4 H.sub.2 PO.sub.4 +MgO→MgNH.sub.4 PO.sub.4 +H.sub.2 O
Heating: 2MgNH.sub.4 PO.sub.4 →Mg.sub.2 P.sub.2 O.sub.7 +H.sub.2 O+2NH.sub.3
In various working techniques, for example, in the preparation of investment compound models for making model-casting structures or in the preparation of refractory individual stumps, casts of dental engineering models, which frequently consist of plaster as the model material, are sometimes made, and these are then filled with the investment compounds described above, the investment compound solidifying in this cast mass. This method is also known under the term "duplicating". Inter alia, aqueous agar compositions or else the increasingly used silicone duplicating materials, which give a very accurate reproduction true to shape, are known as duplicating materials. During the solidification reaction, after the completion thereof and the release of the resulting investment compound model from the silicone duplicating cast mass, the efflorescences, which have already been mentioned above and which are basically precipitations of crystalline alkali metal phosphates, frequently occur on the surface of the investment compound models.
The alkalis presumably originate mainly from the additives which are added for stabilization to the silica sol solutions used as mixing fluids, or they originate from the alkali metal phosphate additives which are added to the investment compound powder formulations for controlling the setting kinetics.
These so-called "efflorescences" can adversely affect the accuracy of the fit of the tooth replacement parts prepared on the basis of such investment compound models, so that it is necessary to avoid the "efflorescences".
There has been no lack of attempts at preventing these efflorescences. It is known that investment compound formulations with markedly changed setting kinetics and a lower setting temperature have been improved in this respect; however, these formulations cannot be used opposite agar-based duplicating gel, since adhesions of investment compound to the agar duplicating materials occur at the low setting temperatures. This means that these investment compound formulations can then no longer be universally used for duplicating materials of silicone and agar, so that the applicability is greatly restricted.
Another attempt at suppressing the "efflorescences" is described in EP-0,417,527. In this case, the addition of 0.01 to 10% by weight of at least one solid organic acid soluble in water and/or alcohol and having 2 to 10 carbon atoms is recommended in the preparation of casting moulds from casting investment compounds.
These organic compounds which are combustible at the usual preheating temperatures can lead to a weakening of the ceramic structure and effect an increase in the expansion on setting, which adversely affects the accuracy of the fit of the finished workpiece. Added quantities of the order of 1.2% by weight already effect a significant lowering of the setting temperature and a marked increase in the setting time, which prevent universal application for duplicating materials of silicone and agar gel.
An addition of 5.0% by mass of citric acid to an investment compound consisting of 42.0% by weight of quartz sand, 25.0% by weight of cristobalite powders, 9.1% by weight of magnesium oxide, 8.0% by weight of phosphates, 0.5% by weight of coloured pigments and 10.4% by weight of quartz powder gives a composition which, with a quantity of mixing fluid of 17 ml of silica sol solution per 100 g of powder, does not lead to any workable consistency, because of extremely slow hardening reaction and a very inhomogenous hardening.
It has been found that the object underlying the invention is achieved by the addition of zeolites to the investment compounds known per se.
The zeolites are preferably employed in quantities from 0.1 to 10.0% by weight (relative to the total pulverulent compound before the addition of the mixing fluid), particularly preferably in quantities from 0.4 to 5.0% by weight.
Zeolites to be employed preferably according to the invention are characterized by the general formula (I):
M.sup.1 n[mM.sup.2 O.sub.2 ×n SiO.sub.2 ]×qH.sub.2 O
where:
M1 denotes one equivalent of an exchangeable cation, whose number corresponds to the proportion of M2,
M2 denotes a trivalent element which, together with the Si, forms the oxide skeleton of the zeolite,
n/m denotes the SiO2 /M2 O2 ratio and
q denotes the quantity of the adsorbed water.
From their fundamental structure, zeolites are crystalline alumosilicates which are built up from a network of tetrahedra of SiO4 and M2 O4. The individual tetrahedra are mutually linked by oxygen bridges via the corners of the tetrahedra and form a spatial network which is evenly penetrated by channels and voids.
The individual zeolite structures differ by the arrangement and size of the channels and voids and by their composition. To balance the negative charge of the lattice, which arises from the proportion of M2, exchangeable cations are incorporated. The adsorbed water phase qH2 O is reversibly removable, without the skeleton losing its structure.
M2 is in many cases aluminium, but it can also be partially or wholly substituted by other trivalent elements.
A detailed description of zeolites has been given, for example, in the monograph by D. W. Breck "Zeolite Molecular Sieves, Structure, Chemistry and Use", J. Wiley & Sons, New York, 1974.
For example the following zeolites are particularly suitable for the process according to the invention: faujasites, mordenites, zeolite A, zeolite β, zeolite Ω, zeolite L, offretite, ZSM 12, pentasils, PSH-3, ZSM 22, ZSM 23, ZSM 48, EU-1, zeolite T, chabasites, gmelinites, ferrierites, zeolite rho, ZK-5 and others.
The zeolites suitable for the process according to the invention can contain alkali metal cations, such as, for example, Li, Na, K or Rb, or alkaline earth metal cations, such as, for example, Mg, Ca or Sr, or else other cations, such as, for example, H, NH4, Zn, Cu, Ni, Co, Mn, rare earth metals and others. Mixed forms can also be used.
In a particularly preferred embodiment, the zeolites used according to the invention are those in which at least a part of the metal cations has been exchanged for hydrogen ions, preferably 50 to 100%, particularly preferably 80 to 100% of all the exchangeable metal cations originally present.
Particularly preferred for the process according to the invention are zeolites having a multiplicity of acidic centres, such as are formed, for example, by treating zeolites of the faujasite structure with ammonium salt solutions or rare earth salt solutions and subsequent thermal treatment. The added quantity of the zeolites described above is preferably a quantity from 0.1 to 10% by weight. The efflorescence-preventing effect of various zeolite types is pronounced to different extents. Simple experiments allow optimum dosage. The zeolites containing alkali metal, alkaline earth metal or rare earth metal are very effective. The most effective zeolites are those of the H-zeolite Y-type.
For H-zeolite Y, 0.3 to 1.5% by weight was found to be a particularly preferred quantity for obtaining the efflorescence-preventing effect and, for the zeolites containing a rare earth metal, the particularly preferred added quantity is 0.7 to 2.0% by weight.
The basic formulations of the investment compound powders according to the invention can be prepared in a conventional manner known per se in a suitable mixing unit, for example a Nauta mixer, Lodige mixer or the like, in which the pulverulent additives including the zeolites are mixed together one after the other. It is also possible, however, to prepare master mixtures which contain the zeolite, and to mix in these master mixtures. Furthermore, it is also possible with the zeolite-containing investment compound formulations according to the invention, which have been described, to spray these in a manner known per se with isoparaffins, without losing the desired properties described above, for example in order to improve their flow properties once again.
In terms of application, the zeolite-containing investment compound powder mixtures according to the invention show no disadvantages as compared with investment compound mixtures not containing zeolite. No changes in the setting time and setting temperature, relevant to processing, occur. The good gel compatibility is unchanged. The good mechanical strength of the casting muffle or of the model made from the investment compound is unchanged, and the same applies to the expansion on setting, which is an important parameter for the degree of the dimensional accuracy of the casting obtained later.
The investment compound formulations according to the invention can be used, in particular, both opposite duplicating silicone and opposite an agar duplicating composition.
However, the efflorescences described above do not arise when the investment compounds according to the invention are used, so that considerably more precise castings are obtained with the aid of them.
The examples which follow explain the invention.
The expansion on setting, the processing time and the compressive strength are determined analogously to DIN 13919, part 2, June 1984. The setting time is the point in time at which the setting temperature reaches the temperature maximum. The tendency to efflorescence was tested by mixing the investment compound powders described with a commercially available silica sol mixing fluid (Levotherm mixing fluid) and pouring the mixed casting investment compound paste into an addition-crosslinked silicone duplicating moulding compound (for example of Tecnovil commercial material), by releasing the solidified investment compound model and assessing the investment compound surface 24 hours after mould release and standing in room air. The investment compound powder composition is prepared by homogeneous mixing of the individual components in a slow-blade mixer (Lodige mixer), a conical truncated cone mixer with revolving screw (Nauta mixer) or in tumble mixers, but other suitable mixer units can in principle also be used. The examples given below are intended to describe the invention, without restricting it by the description of these examples.
The constituents of phosphate-bonded casting investment compounds are described, for example, in K. Eichner, Zahnarztliche Werkstoffe und ihre Verarbeitung [Dental Materials and their Processing], volume 1, Huthig Verlag, Heidelberg, 1981, page 42, or, for example, in: Quintessenz Zahntechnik 17, 73-86 (1991).
The quartz powder used in the examples has an SiO2 content of >99% with a total residue of about 90% by volume at a grain diameter of 2 μm, measured by means of a Cilas granulometer, and a total residue of about 89% by weight at a sinking velocity-equivalent diameter of 2.5 μm, measured by sedimentation analysis by means of a Sedi Graph 5100. A usable type of quartz sand has an SiO2 content of >99% at a mean grain size of 0.28 mm. A cristobalite powder type which can be used shows, at an SiO2 content of >99%, a grain size distribution by screen analysis of (diameter/proportion in % by weight) >200 μm/0.5, >100/5, >63/20, >40/44, <40/30.5 and a BET surface area of 0.9 m2 /g. The phosphates used are Fabutit 746 (made by Budenheim) in a addition to a little Fabutit GI/66A (made by Budenheim), and the magnesium oxide used is Dynamag K (made by Huls) in addition to a little Mag Chem 40 (Gobel & Pfrengle). For colouring the compound, a red dyestuff (made by Conrads) was used, which on average has the following composition: 53.9-51.6% of SiO2, 24.0-27.4% of Al2 O3, 6.3-11.6% of Fe2 O3 and 0.8-0.21% of MgO, loss on ignition 12.5-8.5%.
Various investment compounds mixed with silica sol solution were assessed, after solidification in the silicone mould, for their efflorescence behaviour opposite duplicating silicone (SE=rare earth metal):
__________________________________________________________________________
1 2 3 4 5
__________________________________________________________________________
Compo- 40.0 quartz
40.0 quartz
40.0 quartz
42.0 quartz
42.0 quartz
sition sand sand sand sand sand
of the 25.0 cristo-
25.0 cristo-
25.0 cristo-
25.0 cristo-
25.0-cristo-
invest- balite balite
balite
balite
balite
ment 9.4 magne-
9.4 magne-
9.4 magne-
9.4 magne-
9.1 magne-
compound
sium oxide
sium oxide
sium oxide
sium oxide
sium oxide
powders 8.0 phos-
8.0 phos-
8.0 phos-
8.0 phos-
8.0 phos-
[% by phates phates
phates
phates
phates
weight] 17.6 quartz
17.1 quartz
16.6 quartz
0.5 dyestuff
14.4 quartz
powder powder
powder powder
(comparison
0.5 H-
1.0 H-
13.1 quartz
1.0 H-
mixture)
zeolite Y
zeolite Y
powders
zeolite Y
2.0 H-
0.5 dyestuff
zeolite
Y
Efflorescences
yes no no no no
__________________________________________________________________________
6 7 8 9
__________________________________________________________________________
Compo,- 42.0 quartz
42.0 quartz
42.0 quartz
42.0 quartz
sition sand sand sand sand
of the 25.0 cristo-
25.0 cristo-
25.0 cristo-
25.0 cristo-
invest- balite balite balite balite
ment 9.1 magne-
9.1 magne-
9.1 magne-
9.1 magne-
compound sium oxide
sium oxide
sium oxide
sium oxide
powders 8.0 phos-
8.0 phos-
8.0 phos-
8.0 phos-
[% by phates phates phates phates
weight] 0.5 dyestuff
0.5 dyestuff
0.5 dyestuff
0.5 dyestuff
12.9 quartz
15.4 quartz
14.4 quartz
14.2 quartz
powder powder powder powder
1.0 H- (comparison
0.5 SE-
1.2 SE-
zeolite Y
mixture)
zeolite Y
zeolite Y
1.5 iso- 0.5 NaCl
eicosane
Efflorescences
no yes no no
__________________________________________________________________________
The tests also show that an addition of isoparaffin does not impede the efflorescence-preventing properties of the addition of zeolites.
In the experiments of this example, a standard investment compound mixture (=S) having the following composition is used.
S: 42.0 parts by weight of quartz sand
25.0 parts by weight of cristobalite powder
9.1 parts by weigh of magnesium oxide
8.0 parts by weight of phosphates
15.9 parts by weight of quartz powder
__________________________________________________________________________
Composition
S S + 1.5
S + 1.5
S + 1.5
S + 2
S + 3
of the parts by
parts by
parts by
parts by
parts by
investment
weight of
weight of
weight of
weight of
weight of
compound H-zeolite Y
K/Na K-zeolite L
Ca- K-zeolite Y
zeolite A zeolite Y
Degree of
5 1 1-2 2-3 1 2
the
efflores-
cences*.sup.)
__________________________________________________________________________
*.sup.) 5 = pronounced efflorescences
4 = moderate efflorescences on the front and/or rear of the model
3 = slight efflorescences on the front and/or rear of the model
2 = very slight efflorescences, mainly on the rear of the model
1 = no efflorescences
The addition, according to the invention, of zeolites to the investment compound powder shows extensive improvements in the tendency not to efflorescence in all cases, as compared with the mixture S.
__________________________________________________________________________
Physical data of invesitment compound samples
__________________________________________________________________________
Composition of the
42.0 quartz sand
42.0 quartz sand
42.0 quartz sand
investment compound
25.0 cristobalite
25.0 cristobalite
25.0 cristobalite
powders powder powder powder
[% by mass]
9.1 magnesium
9.1 magnesium
9.1 magnesium
oxide oxide oxide
8.0 phosphates
8.0 phosphates
8.0 phosphates
0.5 dyestuff
0.5 dyestuff
0.5 dyestuff
15.4 quartz powder
1.0 H-zeolite Y
0.5 citric acid
(comparison sample)
14.4 quartz powder
14.9 quartz powder
(comparison sample)
Powder: Levotherm
silica sol mixing
100 g: 16 ml
100 g: 16 ml
100 g: 16 ml
fluid
Process time
3.5 3.5 5.5
(minutes)
Setting time
5.75 6.0 8.0
(minutes)
Setting temperature
71.0 70.0 69.0
(°C.)
Expansion on setting
0.2 0.2 0.7
(%)
Compressive strength
14.7 17.5 10.2
at room temperature
(N/mm.sup.2)
__________________________________________________________________________
The zeolite addition according to the invention does not cause any adverse influence on the compatibility with duplicating gel and on the expansion on setting. In addition, the mechanical properties have been improved due to the zeolithe addition.
Claims (8)
1. Casting phosphate-bonded investment compound powders, comprising, in addition to refractory materials and binders, zeolites in an amount of from 0.1 to 10% by total weight.
2. Casting phosphate-bonded investment compounds according to claim 1, wherein said zeolites are present in an amount of from 0.3 to 2.0% by total weight.
3. Casting phosphate-bonded investment compounds according to claim 1, wherein said zeolites are present in an amount of from 0.7 to 1.5% by total weight.
4. Casting phosphate-bonded investment compounds according to claim 1, wherein the zeolites represent one or more zeolites selected from the group consisting of faujasites, mordenites, zeolite β, zeolite Ω, zeolite L, zeolite A, offretite, ZSM 12, pentasils, PSH-3, ZSM 22, ZSM 23, ZSM 48, EU-1, zeolite T, chabasites, gmelinites, ferrierites, zeolite rho and ZK-5.
5. Casting phosphate-bonded investment compounds according to claim 1 wherein said zeolite is one or more acidic types of faujasite structure.
6. Casting investment compounds according to claim 1 in the form of a powder mixture.
7. Casting investment compounds according to claim 1, in the form of a mixture obtained by dough-forming with a suitable aqueous or alcoholic mixing fluid.
8. Investment compound models, made from casting phosphate-bonded investment compounds according to claim 1.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4319187.8 | 1993-06-09 | ||
| DE4319187A DE4319187A1 (en) | 1993-06-09 | 1993-06-09 | Casting investment materials |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US5520726A true US5520726A (en) | 1996-05-28 |
Family
ID=6490008
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US08/252,868 Expired - Fee Related US5520726A (en) | 1993-06-09 | 1994-06-02 | Casting investment compounds |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US5520726A (en) |
| EP (1) | EP0629458B1 (en) |
| JP (1) | JPH0796347A (en) |
| AT (1) | ATE159876T1 (en) |
| CA (1) | CA2125252A1 (en) |
| DE (2) | DE4319187A1 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2779425A1 (en) * | 1998-06-05 | 1999-12-10 | Didier Frot | Refractory powder composition e.g. for wax foundry, for dental applications, for silversmith's trade |
| RU2178406C2 (en) * | 1995-04-20 | 2002-01-20 | Рон-Пуленк Фибер э Резэн Энтермедиат | Method of butadiene oxycarbonylation |
| US20100142503A1 (en) * | 1995-10-05 | 2010-06-10 | Kubler Joseph J | Hierarchical Data Collection Network Supporting Packetized Voice Communications Among Wireless Terminals And Telephones |
| US20110232857A1 (en) * | 2010-03-23 | 2011-09-29 | Mcguire Daniel S | Investment Casting Shell Incorporating Desiccant Material |
| US20150258602A1 (en) * | 2012-10-18 | 2015-09-17 | Cermatco Ltd | Investment Binder and Use of the Investment Binder |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19648329C2 (en) * | 1996-11-22 | 1998-10-22 | Herbert Wittekind | Process for the production of a ceramic mixing vessel and mixing vessel |
| DE102005011019B4 (en) * | 2005-03-10 | 2007-01-04 | Daimlerchrysler Ag | Production and use of a destructible mold core for the metallic casting |
| WO2014021453A1 (en) * | 2012-08-03 | 2014-02-06 | 株式会社豊田自動織機 | Active substance, method for manufacturing active substance, and lithium-ion secondary cell |
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-
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- 1994-05-27 AT AT94108194T patent/ATE159876T1/en active
- 1994-05-27 DE DE59404505T patent/DE59404505D1/en not_active Expired - Fee Related
- 1994-05-27 EP EP94108194A patent/EP0629458B1/en not_active Expired - Lifetime
- 1994-06-02 US US08/252,868 patent/US5520726A/en not_active Expired - Fee Related
- 1994-06-03 JP JP14404894A patent/JPH0796347A/en active Pending
- 1994-06-06 CA CA002125252A patent/CA2125252A1/en not_active Abandoned
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2178406C2 (en) * | 1995-04-20 | 2002-01-20 | Рон-Пуленк Фибер э Резэн Энтермедиат | Method of butadiene oxycarbonylation |
| US20100142503A1 (en) * | 1995-10-05 | 2010-06-10 | Kubler Joseph J | Hierarchical Data Collection Network Supporting Packetized Voice Communications Among Wireless Terminals And Telephones |
| FR2779425A1 (en) * | 1998-06-05 | 1999-12-10 | Didier Frot | Refractory powder composition e.g. for wax foundry, for dental applications, for silversmith's trade |
| US20110232857A1 (en) * | 2010-03-23 | 2011-09-29 | Mcguire Daniel S | Investment Casting Shell Incorporating Desiccant Material |
| US20150258602A1 (en) * | 2012-10-18 | 2015-09-17 | Cermatco Ltd | Investment Binder and Use of the Investment Binder |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0796347A (en) | 1995-04-11 |
| CA2125252A1 (en) | 1994-12-10 |
| ATE159876T1 (en) | 1997-11-15 |
| DE59404505D1 (en) | 1997-12-11 |
| EP0629458B1 (en) | 1997-11-05 |
| DE4319187A1 (en) | 1994-12-15 |
| EP0629458A1 (en) | 1994-12-21 |
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